Bent-arm multiband dipole antenna wherein overall dimension is quarter wavelength on low band



Jan. 11, 1966 D. o. MORGAN 3,229,298

BENT-ARM MULTIBAND DIPOLE ANTENNA WHEREIN OVERALL DIMENSION IS QUARTER WAVELENGTH ON LOW BAND Filed NOV. 27, 1962 6 l2 l6 I6 l3 r a 4 1 I l P P /I 1 A h i I6 2 66 M6 8 i P y- 5o w 570 ff .3 ft

1 .Z -4 40 as 1 J 4| 6O 1 48 UT 1 yso I 5 Lav 1 g 54 l I .43 i 1 fi 56 1 G 58 1 INVENTOR 580 Dean 0. Morgan ATTORNEY United States Patent 3,229,298 BENT-ARM MULTIBAND DIPOLE ANTENNA WHEREIN OVERALL DIMENSION lS QUAR- TER WAVELENGTH 0N LOW BAND Dean 0. Morgan, 8697 Highgate Road, Alexandria, Va. Filed Nov. 27, 1962, Ser. No. 240,280 8 Claims. (Cl. 343-806) The present invention relates to improvements in radiant and electromagnetic energy, and more particularly to an antenna for use in radio communication for the transmission and reception of radio frequency energy such as monopoles and dipoles as well as other types of radiators.

The primary object of the invention is to provide an antenna wh ch is designed to reduce the physical length approximately fifty percent or more of the required antenna length without the usual reduction in efiiciency.

Another object is to provide an antenna design which is adapted to be operated on a multiplicity of predetermined frequencies without requiring any changes in the tuning of the antenna or system either mechanically or electrically.

Another object is to provide an antenna of the above mentioned type in which the use of coils, stubs, traps, splines or lumped elements, such as top loading is completely eliminated, yet providing an antenna which is highly efficient.

Another object is to provide means to strengthen and reinforce the radiator structure having increased stability and greater strength than is obtainable in known antenna designs now in use.

Another object is to provide means to vary the operable band width over and above that presently known in conventional antennas reduced to the same physical size.

Another object is to provide an antenna such as a monopole or dipole which will operate on at least two frequency bands without requiring the use of tuning devices and the like whereby the antenna will efiiciently operate on at least two different predetermined frequencies and band widths.

Another object is to provide an antenna of the above mentioned type which can be considerably reduced in weight, size and cost and to enable the antenna to be limitless on power handling Capability without critical induction and capacitance elements.

Another object is to provide an antenna which will be highly efficient at any frequency where linear or lump loaded elements previously have been or could be used.

Another object is to provide an antenna of the monopole or dipole type which can be altered by a relatively simple addition so that the same can operate at frequencies heretofore found to be impractical, ineflicient or impossible to radiate effectively.

Another object is to provide an antenna design which is adapted to control the radiation resistance at the feed point such that coaxial and balanced feed lines can be used without requiring the necessity of auxiliary matching systems and thus cover a single or multiple band of frequencies.

Another object is to provide sizeable gain when operated at or near half wave or multiples thereof without greatly increasing the space requirements as would be necessary in presently known types of antennas.

Another object is to provide an antenna of the monopole or dipole type having a phase reversal section which is essentially lossless and which will give outstanding performance on all bands.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawing wherein:

3,229,298 Patented Jan. 11, 1966 FIGURE 1 is a schematic View showng a dipole antenna arranged in accordance with the present invention.

FIGURE 2 is a schematic view of a slightly modified form of the invention showing a dipole antenna in which the outer section is folded on itself and extends between a pair of spaced conductors.

FIGURE 3 is a schematic view of a still further modified form of the invention showing an antenna of the monopole type in which the conductor is formed into a series of sections and arranged similar to one of the poles shown in FIGURE 1.

FIGURE 4 is a schematic view of a still further modified form of the invention in which the conductor is formed basically into two sections and arranged in a vertical fashion, with additional sections shown by dotted lines.

In the drawing, and more in detail, attention is directed to FIGURE 1 wherein there is shown a particular embodiment of the invention and wherein the reference character 6 will be employed to generally designate a dipole constructed in accordance with the present invention which is excited by a radio frequency generator 5 at frequencies of approximately 7.2 and/ or 3.8 mcs. which is connected by the usual transmission line to oppositely extending legs 7 and 8 equal in total length to approximately 66 feet. The legs 7 and 8 are formed of wire conductors and are bent back upon themselves as at it and 10 to extend inwardly to a point in juxtaposed relation to the generator point 5. The legs and 10 are then return bent and folded back to extend oppositely and in opopsed relation in conductor portions 12 and 13, said conductor portions 12 and 13 terminate at points near, or extending beyond the fold bends 14 and 15 between the legs 7 and 9 and 8 and 10 respectively.

The dipole 6 is formed of 40% copper weld wire of a suitable gauge and can be made of No. 18 gauge wire. If desired, the wire can be larger or thinner depending upon the use and the circuit arrangement of the apparatus. The wire conductors forming the legs 7 to 13 inclusive are closely spaced a distance equal to /2 to 4 inches or more, and the total length of the dipole can be equal to fractional parts of a full wave length divided by 2.

In construction, the conductors of the dipole are spaced by suitable insulators 16, and the same can be suspended from a supporting arm or pole. Also, the conductors 7 and 8 can be formed of tubular or bar stock of sufiicient rigidity to support the legs 94!) and 12-13, which may be made of wire or tubing and can be of the same or different size than the conductors 7 and 8.

Thus, there is provided a dipole which will be resonant at its /2 wave mode and will also be resonant at .a frequency somewhat greater than V2 its /2 wave frequency. The dipole described above also becomes very effective as a wave radiator. This is attributed to the fact that the conductors are folded in closely spaced relation and extend substantially equal lengths from their terminus ends inwardly to the generator 5 or a point located adjacent the generator. It will be seen that the dipole has been considerably shortened Without disturbing the other normal modes, and it is seen that the conductors 10 and 13 lowers the frequency of /4 wave resonance to be approximately /2 the /2 wave frequency, and thus can be operated as a true 2 4 wave dipole.

The dipole shown in FIGURE 1 may be fed at the center in a conventional manner and operated on two frequency bands at approximately one octave separation without requiring the use of capacitors, coils, traps or stubs of any kind. The VSWR was found to be under 2 to l USWR with a band width of approximately 4% of the 2 to l, the gain of such an antenna is considerably better than an ordinary dipole at its half wave mode being in excess of 7% of frequency and is about of a full dipole at its wave mode. It is obvious that a dipole antenna is formed in which the radiated power is substantially more uniform from the generator to the terminus end and there is thus provided a more nearly constant current amplitude over the radiator. Thus the radiation resistance at 5 is nearly the same at both resonant frequencies.

In another form of the invention shown in FIGURE 2 there is shown a dipole which is excited by a generator 50 connected to oppositely extending legs and 21 similar to the conductors 7 and 8 shown in FIGURE 1. However, the conductor legs 20 and 21 are provided with ofi'fset portions 23 and 24 at the ends thereof which are connected to conductors 25 and 26 similar to the conductors 9 and 10 in FIGURE 1. The conductors 25 and 26 extend inwardly to the point of the generator 511 along the full length of the dipole conductors 20 and 21 and are then folded on themselves as at 28 and extend outwardly in auxiliary leg portions 30 and 31 arranged between the dipole conductors 20-21 and 25-26 and terminate in close proximity to the end portions 23 and 24. The dotted line 35 indicates the amplitude curve of the instantaneous current distribution throughout the dipole at A wave resonance which indicates the effectiveness of providing the in and out folded sections 25-30 and 2631 of the respective segments 20 and 21. Nearly the same current distribution is present in the form of the invention shown in FIGURE 1. Y

In the form of the invention shown in FIGURE 3 there is shown a monopole antenna generally designated which is excited by a conventional radio frequency generator 5" provided with a suitable ground connection to the ground G and connected to a monopole type antenna 41 across the insulator 43 by the transmission line. The monopole 41 is formed of a copper conductor similar to that previously described and will have an impedance across the insulator 43 and will have a radiation characteristic in accordance with the length of the radiator 1 depending upon the wave length and energy generated by the generator 5". In a particular case the monopole 40 was of an adjustable height between 17 to 33 feet equal to fractional parts of a full wave length of 360. The monopole 41 is provided with a downwardly extending leg portion 44 which extends from the terminus end 45 'to a point as at 46 adjacent the point of transmission line connection from the generator 5" and where it is return bent on itself to extend parallel with an upstanding con ductor 48 which terminates at, near or beyond the terminus end 45. The conductors 41, 44 and 48 are spaced by suitable separators formed of dielectric material such as plastic or plastic thermosetting composition similar to the insulator 16 shown and described in connection with the form of the invention shown in FIGURE 1.

In the monopole structure it was found that the measured radiation resistance of the three-fold monopole was not less than 45 ohms or more than 65 ohms at both resonances and in measurements made it was found that when tuned to 7.1 mcs. and 14.2 mcs. these conditions existed. It was apparent that no lumped loading of any type is employed and that the conductors can be arranged in a zig-zag fashion extending to the proper wave length and can be closely spaced one from the other of between /2 to 4 inches or more in distance. The conductor sections 41, 44 and 48 can be increased or decreased in unison or separately, and it can be stated that when decreased, the resonate frequency will increase linearly with the change in length and will occur with an increase in the fundamental mode by a corresponding amount. With the exception of the frequency change no other changes will occur that will effect the impedance of the radiator or its radiation characteristics.

Instead of three folds shown in FIGURE 3 a greater or smaller number can be used and can be extended to include 4, 5 and 6 folds, and it will be found that as the number of conductors increased the current amplitude will become more uniform throughout the radiator. It

was found that using 6 conductors and conventional measuring instruments the usually great difference in current amplitude throughout the radiator was drastically reduced and essentially little change in current amplitude of appreciable moment could be measured throughout the length of the conductors and the radiated power from the antenna increased with each added conductor.

In FIGURE 4 there is illustrated another embodiment of the invention including a modified dipole antenna generally designated 50 which is excited by a conventional radio frequency generator 5" connected to oppositely extending conductor legs 51 and 52 similar to the conductors 7 and 8 shown in FIGURE 1. However, the conductor legs 51 and 52 are provided with offset conductor leg portions 53 and 54 which extend substantially the entire length of the conductors 51 and 52 and have their inner ends connected to an insulator 60 at the same point of connection that the generator 5 is connected to the legs 51 and 52, Additional elements 57 and 58 are connected to the return bent portion 56 and are indicated as at FIGURE 4. All conductors are made of inch aluminum tubing and the total length from point 57a to 58a is approximately 16 feet 7.5 inches with the length of extensions 57 and 58 each being approximately 12% of the total length, and the spacing between conductors 52 and 54, as well as 51 and 53, being approximately 4 inches. When the antenna is fed at the point 5" by a cable of approximately 52 ohms impedance at a frequency of substantially 29 megacycles the VSWR was found to be under 1.5 to l with a band width of approximately plus or minus 4% to the 2.1 VSWR. By direct substitution of a tuned dipole the gain was found to be approximately 2 /2 decibels and the pattern was of cardiod shape. A further section of approximate ly the same duplicated length of conductors as shown by the dotted lines gives a further increase in gain averaging 2.5 decibels or 5 decibels total. This procedure of adding elements can be carried to infinity each section adding more gain and increasing the VSWR band width, until no electromagnetic energy is left in the conductors. Thus, exceptional gains can be achieved in a relatively small space.

As in the case set forth in the forms of the invention shown in FIGURES 1 and 2 it is pointed out that a folded radiator of the type shown in FIGURE 3 can be tuned to any lower frequency while the physical length of the radiator is held constant, and the feeder used can have any reasonable impedance and that a low VSWR can be achieved at any frequency.

It is pointed out that in all forms of the invention there IS provided a conductor of a predetermined wave length having zig-zag portions or folded conductor sections which are closely spaced, and in which the conductor sections extend outwardly from the generator and are then folded back and forth from a predetermined distance between the limits of the terminus end and the generator, and that the conductor sections are closely spaced and substantially parallel, and generally open at the center.

It is to be understood that the forms of the invention herewith shown and described are to .be taken as preferred embodiments thereof and that various changes in the length, number of conductors and other parts may be resorted to without departing from the spirit of the invention or the scope of the subj-oined claims.

What I claim is:

1. An antenna operative over a plurality of bands of frequencies adapted to be fed by a radio frequency generator, comprising at least one conductor of copper weld wire of relatively small gauge having one end connected to said generator, said conductor being provided with a return bent portion forming a second conductor of a length substantially equal to said first named conductor and extending in closely spaced parallel relation therewith for its entire length extending along the entire length of said conductor and terminating in an open condition at a point in close proximity to said connection point of the generator, such that at the lowest frequency band of operation the overall length of the antenna is substantially reduced over that of a resonant quarter or half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and quarter wave overall length when compared to a half wave antenna and quarter wave and eighth wave overall length when compared to a quarter wave antenna, while yet maintaining a reasonable impedance match at both frequency bands of operation without the use of auxiliary matching networks.

2. An antenna operative over a plurality of bands of frequencies adapted to be fed by a radio frequency generator of predetermined impedance, comprising a conductor having one end connected to said generator, at second conductor extending parallel with and spaced from said first named conductor, a connection between the outer end of said first conductor and second conductor and said second conductor extending along substantially the entire length of said first conductor and terminating in an open condition at a point in close proximity to said generator, such that at the lowest frequency band of operation the overall length of the antenna is substantially reduced over that of a resonant quarter or half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and quarter wave overall length when compared to a half wave antenna and quarter wave and eighth wave overall length when compared to a quarter wave antenna, while yet maintaining a reasonable impedance match at .both frequency bands of operation without the use of auxiliary matching networks.

3. An antenna operative over a plurality of bands of frequencies adapted to be fed by a radio frequency generator of predetermined impedance, comprising a conductor bent upon itself in a zigzag fashion to form at least one leg portion, said leg portion extending the full length of said main conductor and terminating in an open condition at a point adjcacent the outer end of said conductor in one of said zig-Zag areas, such that at the lowest frequency band of operation the overall length of the antenna is substantially reduced over that of a resonant quarter or half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and quarter wave overall length when compared to a half wave antenna and quarter wave and eighth wave overall length when compared to a quarter wave antenna, while yet maintaining a reasonable impedance match at both frequency bands of operation without the use of auxiliary matching networks.

4. A high gain antenna operative over a plurality of bands of frequencies adapted to be fed by a generator of predetermined impedance, comprising a first linear conductor having one end connected to said generator, a second linear conductor having one end connected to the outer end of said first conductor and its other end terminating at a point in close proximity to the point of connection of said first conductor with said generator, such that at the lowest frequency band of operation the overall length of the antenna is substantially reduced over that of a resonant quarter or half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and quarter wave overall length when compared to a half wave antenna and quarter wave and eighth wave 6 overall length when compared to a quarter wave antenna, while yet maintaining a reasonable impedance match at both frequency bands of operation without the use of auxiliary matching networks.

5. A high gain antenna operative over a plurality of bands of frequencies adapted to be fed by a radio frequency generator, having a predetermined impedance, comprising a first linear conductor having one end connected to the generator, a second linear conductor with one end connected to the outer end of said first conductor and its other end terminating at a point in close proximity to said generator, and a third linear conductor connected to the last named end of the second conductor and extending individually parallel spaced relation with said first conductors, such that at the lowest frequency band of operation the overall length of the antenna is reduced by proportions approaching 50% of that of a resonant quarter wave antenna while yet another separate band of frequencies of operation is provided at a higher frequency determined by a'fractional part of the total length of said conductors, said antenna being operational at substantially quarter wave and one eighth wave overall length while yet maintaining a reasonable impedance match at both frequency bands of operation without the use of auxiliary matching networks.

6. A high gain antenna operative over a plurality of bands of frequencies comprising a pair of linear conductors, a radio frequency generator having a predetermined impedance connected to the inner ends of said conductors, and a second pair of conductors having one end connected to the ends of the first named conductors remote from said generator and extending individually parallel to the first pair of conductors in a direction inwardly to a point in close proximity to said generator, such that at the lowest frequency band of operation the overall length of the antenna is substantially reduced over that of a resonant half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and one quarter wave overall length while yet maintaining a reasonable impedance match at both frequency bands of operation without the use of auxiliary matching networks.

7. A high gain antenna operative over a plurality of bands of frequencies adapted to be fed by a radio frequency generator having a predetermined impedance, comprising a pair of linear conductors with their inner ends connected to said generator, a second pair of conductors arranged parallel to said first conductors with their outer ends connected to the outer end of said first conductors, and a third pair of conductors connected to the inner ends of said second conductors and arranged to extend outwardly in closely spaced parallel relation with said first and second conductors, said third pair of conductors being arranged intermediate said first and second conductors, the second and third pairs of conductors being individually parallel with the first pair of conductors and not to each other, such that at the lowest frequency band of operation the overall length of the antenna is reduced by proportions approaching 50% of that of a resonant half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and quarter wave overall length While yet maintaining a reasonable impedance match at both frequency bands of operation without the use of auxiliary matching networks.

8. A high gain antenna operative over a plurality of bands of frequencies adapted to be fed by a radio frequency generator having a predetermined impedance, comprising a pair of linear conductors with their inner ends connected to said generator, a second pair of linear conductors connected to the outer ends of the first named conductors and extending inwardly to a point in close proximity to said generator, and a third pair of linear conductors with their inner ends connected to the second pair of conductors and extending outwardly in parallel closely spaced relation to said second pair of conductors to a terminus point adjacent the connection between said first and second linear conductors, and insulators arranged in spaced relation between said pairs of linear conductors to hold the same in parallel spaced relation said second and third pairs of conductors being individually parallel to said first pair of conductors, such that at the lowest frequency band of operation the overall length of the antenna is reduced by proportions approaching 50% of that of a resonant half wave antenna, while yet another separate band of frequencies of operation is provided at a higher frequency determined by a fractional part of the total length of said conductors, said antenna being operational at substantially half wave and quarter wave overall length while yet maintaining a reasonable impedance match at both frequency .bands of operation without the use of auxiliary matching networks.

References Cited by the Examiner UNITED STATES PATENTS 2,258,406 10/1941 Carter 343-803 2,283,914 5/1942 Carter 343804 2,523,531 9/1950 F'lippen 343803 2,535,298 12/1950 Lattin 343-806 2,647,211 7/1953 Smeby 343--908 2,750,789 6/1956 Harris 343873 2,780,808 2/ 1957 Middlemark 343-908 2,875,441 2/ 1959 McGrane 343806 2,994,876 8/1961 Josephson 343-803 3,167,775 1/ 1965 Guerthler 343908 X OTHER REFERENCES Kraus, Multi-Wire Dipole Antennas, Electronics, volume 13, 1940, pp. 26 and 27 relied on.

HERMAN KARL SAALBACH, Primary Examiner.

ELI LIEBERMAN, Examiner.

R. F. HUNT, Assistant Examiner. 

1. AN ANTENNA OPERATIVE OVER A PLURALITY OF BANDS OF FREQUENCIES ADAPTED TO BE FED BY A RADIO FREQUENCY GENERATOR, COMPRISING AT LEAST ONE CONDUCTOR OF COPPER WELD WIRE OF RELATIVELY SMALL GAUGE HAVING ONE END CONNECTED TO SAID GENERATOR, SAID CONDUCTOR BEING PROVIDED WITH A RETURN BENT PORTION FORMING A SECOND CONDUCTOR OF A LENGTH SUBSTANTIALLY EQUAL TO SAID FIRST NAMED CONDUCTOR AND EXTENDING IN CLOSELY SPACED PARALLEL RELATION THEREWITH FOR ITS ENTIRE LENGTH EXTENDING ALONG THE ENTIRE LENGTH OF SAID CONDUCTOR AND TERMINATING IN AN OPEN CONDITION AT A POINT IN CLOSE PROXIMITY TO SAID CONNECTION POINT OF THE GENERATOR, SUCH THAT AT THE LOWEST FREQUENCY BAND OF OPERATION THE OVERALL LENGTH OF THE ANTENNA IS SUBSTANTIALLY REDUCED OVER THAT A RESONANT QUARTER OR HALF WAVE ANTENNA, WHILE YET ANOTHER SEPARATE BAND OF FREQUENCIES OF OPERATION IS PROVIDED AT A HIGHER FREQUENCY DETERMINED BY A FRACTIONAL PART OF THE TOTAL LENGTH OF SAID CONDUCTORS, SAID ANTENNA BEING OPERATIONAL AT SUBSTANTIALLY HALF WAVE AND QUARTER WAVE OVERALL LENGTH WHEN COMPARED TO A HALF WAVE ANTENNA AND QUARTER WAVE AND EIGHT WAVE OVERALL LENGTH WHEN COMPARED TO A QUARTER WAVE ANTENNA, WHILE YET MAINTAINING A REASONABLE IMPEDANCE MATCH AT BOTH FREQUENCY BANDS OF OPERATION WITHOUT THE USE OF AUXILIARY MATCHING NETWORKS. 